1. Field
The present disclosure relates generally to manufacturing and in particular to a method and apparatus for drilling holes. Still more particularly, the present disclosure relates to a method and apparatus for drilling a hole in a stack of materials.
2. Background
Manufacturing may involve the use of tools and/or labor to create items for use or sale. In aerospace manufacturing, these items may include, for example, without limitation, aircraft, aircraft parts, missiles, rockets, and/or spacecraft. In manufacturing various items, a number of different operations may be performed. For example, without limitation, these operations may include, extrusion, pressing, rolling, piercing, machining, drilling, routing, and curing.
With respect to drilling, a drill may be used to create holes or channels that are typically cylindrical in solid materials. A drill may be a tool with a rotating section that may hold a drill bit to drill holes. A drill bit may be a cutting tool used to create holes in an object. These holes may be, without limitation, cylindrical or non-cylindrical depending on the particular implementation. Drilling may involve drilling a channel, such as a cylindrical hole.
One type of drill that may be used for drilling holes may be a drill with a positive feed feature. This positive feed feature may allow the drill to push the drill bit into the object while drilling occurs. Drills also may be used in which the feed feature may be used to push the drill bit into the object and then retract the drill bit while drilling occurs. This type of forward and reverse motion of the drill bit may provide for a cleaner quality hole. Further, this type of drilling also may reduce the amount of heat applied to the object, which also may increase the quality of the hole.
This type of drilling may be performed with a stackup of materials. A stackup of materials is a set of materials. A set, as used herein, refers to one or more items. For example, a stackup of materials may be one or more layers of different types of materials. A stackup of materials may also be referred to as a stackup. When multiple layers are present in the stackup, one material may require drilling at a first speed, while another material may require drilling at a second speed. For example, without limitation, a titanium layer within the stackup may require a slower drilling speed as compared to a composite layer within the stackup. A stackup may often include a combination of relatively hard and soft layers of materials.
Drilling deep stackups having both hard and soft layers of materials may be very time consuming when the majority of the stackup contains soft materials. Some types of drilling apparatus may allow only for a single drilling speed. This drilling speed may be set prior to drilling into a stackup. With these types of systems, the drilling speed may be set to a slower speed for the set of layers having the hardest material. As a result, the time needed to drill through soft materials may also be increased because of the lower drilling speed. This increased time may occur because the drilling speed may be kept slow to account for a harder material even though the majority of the stackup contains a softer material which may be drilled at a faster speed. The spindle speed may be the speed at which the drill rotates the drill bit, and the feed rate may be the speed at which the drill may advance the drill bit into the material. In these examples, the thrust level may be the reaction force on the drill caused by the spindle speed and/or feed rate.
Other types of drilling apparatus may allow controlling the rotation of the spindle in the drilling apparatus. These types of drilling apparatus may use a mechanical mechanism to detect when a layer having a harder or softer material has been reached. In this type of drilling apparatus, a mechanical sensor may be used to detect changes in thrust levels. An example of a spring washer that may be used in currently available drilling apparatus is a Belleville washer. This type of washer may be used, for example, without limitation, in conjunction with an open air valve, which may change the speed of the drill when a harder material is encountered by the drilling apparatus.
A drawback with this type of washer is that adjustments to the drilling speeds may have to be made constantly because as the drill bit wears, the thrust level applied to the stackup may change.
Therefore, it would be advantageous to have a method and apparatus that overcomes the problem above in drilling holes into a stackup.